CY-404 Operating Systems - Nov 2023 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aList and explain the various features of operating system.
   How to answer

   • Define operating system and its role as resource manager and extended machine
   • List features: process management, memory management, file management, I/O, protection/security, networking, UI
   • Explain each feature briefly with purpose/example
2. 7 Marks
   bDescribe the evolution of operating system in detail.
   How to answer

   • Start from batch systems and multiprogramming
   • Describe time-sharing, personal computers, parallel and distributed systems
   • Describe real-time and modern mobile / networked evolution
3. 7 Marks
   aDiscuss the various services provided by operating system.
   How to answer

   • Define OS services view for user and system
   • Explain program execution, I/O operations, file-system manipulation
   • Explain communication, error detection, resource allocation, accounting, protection
4. 7 Marks
   bExplain the Peterson solution for critical section problem.
   How to answer

   • State critical-section problem requirements: mutual exclusion, progress, bounded waiting
   • Present Peterson's shared variables flag[2] and turn with pseudocode for Pi and Pj
   • Explain proof of correctness and satisfaction of three requirements
5. 7 Marks
   a

   Consider the following set of process, with the length of the CPU burst given in milliseconds.

   Process	Burst Time	Priority
   $P_1$	10	3
   $P_2$	1	1
   $P_3$	2	3
   $P_4$	1	4
   $P_5$	5	2

   The processes are assumed to have arrived in the order $P_1, P_2, P_3, P_4, P_5$ all at time 0. Calculate the turnaround time of each process by applying priority scheduling algorithm.

   How to answer

   • Assume lower number means higher priority; all arrive at time 0
   • Order execution by priority: P2, P5, P1/P3, P4 and draw Gantt chart
   • Compute completion - arrival = turnaround for each process
6. 7 Marks
   bWrite and explain the Banker's algorithm for dead lock avoidance.
   How to answer

   • Define deadlock avoidance and safe state concept
   • Present data structures: Available, Max, Allocation, Need
   • Give safety algorithm and resource-request algorithm steps
   • Illustrate with example of safe sequence check
7. 7 Marks
   aDiscuss the advantage of segmentation over paging.
   How to answer

   • Define paging vs segmentation addressing
   • Compare on logical view, fragmentation, sharing, protection
   • Conclude advantages: no internal fragmentation view, logical units, sharing/protection
8. 7 Marks
   bExplain in brief the need of demand paging.
   How to answer

   • Define demand paging and lazy loading concept
   • Explain need: reduce memory use, faster startup, support large virtual space
   • Mention page fault handling and locality
9. 7 Marks
   aDefine Belady's anomaly. Why does Belady's anomaly happen explain with an example?
   How to answer

   • Define Belady's anomaly: more frames can increase page faults in FIFO
   • Explain why FIFO violates stack property
   • Give classic reference string example e.g. 1,2,3,4,1,2,5... with 3 vs 4 frames
10. 7 Marks
    bSuppose the head of a moving head disk with 200 tracks, numbered 0 to 199, is currently serving a request at track 143 and has just finished a request at track 125. If the queue of requests is kept in FIFO order: 86, 147, 91, 177, 94, 150, 102, 175, and 130. What is the total head movement to satisfy these requests for the FCFS disk scheduling algorithms?
    How to answer

    • Note start head at 143, FIFO order as listed
    • Compute absolute distance for each successive move |next-current|
    • Sum all movements to get total head movement
11. 7 Marks
    aExplain the following with relevant diagrams: Two level directory structure
    How to answer

    • Explain two-level directory: master file directory + per-user UFD
    • Show diagram with MFD pointing to UFDs and files
    • Mention advantages: isolation, searching, no name collision
12. 7 Marks
    bExplain the following with relevant diagrams: Acyclic-graph directory structure
    How to answer

    • Define acyclic-graph directory with shared files/directories
    • Show diagram with links allowing sharing without duplication
    • Discuss issues: deletion, cycle avoidance, reference counting
13. 7 Marks
    aDiscuss in brief the logical structure of I/O function.
    How to answer

    • Define I/O function layers: device, controller, OS interface
    • Explain logical structure: application, device-independent, driver, interrupt handler
    • Mention data path and control flow
14. 7 Marks
    bExplain the interrupt driven I/O techniques.
    How to answer

    • Define interrupt-driven I/O vs programmed I/O
    • Explain steps: issue command, CPU continues, interrupt on completion
    • Discuss advantages, ISR handling and performance
15. 14 Marks
    Discuss in brief any of the following:

    1. a)User level and kernel level threads
    2. b)Virtual memory
    3. c)Tape organization
    4. d)I/O Buffering
    How to answer

    • Choose one topic from a-d as per instruction
    • Give definition and key concepts/components
    • Explain working/advantages with diagram/example if applicable